On tariffs, they could do it with just a simple majority. The rule already is that Congress is generally in charge of tariffs. POTUS has limited control of tariffs in times of national emergencies (ie wars), which Trump declared and is how he has control.
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POTUS can pretty easily start a war on his own though.
Just exercising right under International Emergency Economic Powers Act of 1977.
https://constitutioncenter.org/amp/blog/how-congress-delegates-its-tariff-powers-to-the-president
This is all discussed in the article I linked.
Under the Act, Congress reserved power to override POTUS emergency declaration by joint resolution by both chambers (simple majority).